This invention relates to ink jet printers. In particular, this invention relates to novel designs and methods of manufacture of ink-jet printheads capable of providing ink-droplet-tail-break-off control and preventing meniscus overshoot in order to overcome the puddling, pen directionality, and ruffle problems associated with thermal-ink-jet printing.
The present invention generally relates to printhead structures for use in delivering ink to a substrate, and more particularly to a novel orifice plate designed for attachment to a printhead. The orifice plate includes a number of important structural features that enable high print quality levels to be maintained over the life of the printhead.
Substantial developments have been made in the field of electronic printing, technology. A wide variety of highly efficient printing systems currently exist that are capable of dispensing ink in a rapid and accurate manner. Thermal inkjet systems are especially important in this regard. Printing units using thermal inkjet technology basically involve an apparatus which includes at least one ink reservoir chamber in fluid communication with a substrate (preferably made of silicon [Si] and/or other comparable materials) having a plurality of thin-film heating resistors thereon. The substrate and resistors are maintained within a structure that is conventionally characterized as a xe2x80x9cprintheadxe2x80x9d. Selective activation of the resistors causes thermal excitation of the ink materials stored inside the reservoir chamber and expulsion thereof from the printhead. Representative thermal inkjet systems are discussed in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,771,295 to Baker et al.; U.S. Pat. No. 5,278,584 to Keefe et al.; and the Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988), all of which are incorporated herein by reference.
The ink delivery systems described above (and comparable printing units using thermal inkjet and other ink ejection technologies) typically include an ink containment unit (e.g. a housing, vessel, or tank) having a self-contained supply of ink therein in order to form an ink cartridge. In a standard ink cartridge, the ink containment unit is directly attached to the remaining components of the cartridge to produce an integral and unitary structure wherein the ink supply is considered to be on-boardxe2x80x9d as shown in, for example, U.S. Pat. No. 4,771,295 to Baker et al. However, in other cases, the ink containment unit is provided at a remote location within the printer, with the ink containment unit being operatively connected to and in fluid communication with the printhead using one or more ink transfer conduits. These particular systems are conventionally known as xe2x80x9coff-axisxe2x80x9d printing units. Representative, non-limiting off-axis ink delivery systems are discussed in co-owned pending U.S. patent application Ser. No. 08/869,446 (filed on Jun. 5, 1997) entitled xe2x80x9cAN INK CONTAINMENT SYSTEM INCLUDING A PLURAL-WALLED BAG FORMED OF INNER AND OUTER FILM LAYERSxe2x80x9d (Olsen et al.) and co-owned pending U.S. patent application Ser. No. 08/873,612 (filed Jun. 11, 1997) entitled xe2x80x9cREGULATOR FOR A FREE-INK INKJET PENxe2x80x9d (Hauck et al.) which are each incorporated herein by reference. The present invention (as discussed below) is applicable to both on-board and off-axis systems which will become readily apparent from the discussion provided herein.
In order to effectively deliver ink materials to a selected substrate, thermal inkjet printheads typically include an outer plate member known as a xe2x80x9cnozzle platexe2x80x9d or xe2x80x9corifice platexe2x80x9d which includes a plurality of ink ejection orifices (e.g. openings or bores) therethrough. Initially, these orifice plates were manufactured from one or more metallic compositions including but not limited to gold-plated or palladium-plated nickel and similar materials. However, recent developments in thermal inkjet printhead design have also resulted in the production of orifice plates which are produced from a variety of different organic polymers (e.g. plastics), including but not limited to film products consisting of polytetrafluoroethylene (e.g. Teflon(copyright)), polyimide, polymethylmethacrylate, polycarbonate, polyester, polyamide, polyethylene-terephthalate, and mixtures thereof. A representative polymeric (e.g. polyimide-based) composition which is suitable for this purpose is a commercial product sold under the trademark xe2x80x9cKAPTONxe2x80x9d by E.I. du Pont de Nemours and Company of Wilmington, Del. (USA). Orifice plate structures produced from the non-metallic compositions described above are typically uniform in thickness and highly flexible. Likewise, they provide numerous benefits ranging from reduced production costs to a substantial simplification of the overall printhead structure that translates into improved reliability, economy, and ease of manufacture.
The fabrication of polymeric/plastic film-type orifice plates and the corresponding production of the entire printhead structure is typically accomplished using conventional tape automated bonding (xe2x80x9cTABxe2x80x9d) technology as generally discussed in U.S. Pat. No. 4,944,850 to Dion. Additional information regarding polymeric, non-metallic orifice plates of the type described above is provided in the following U.S. Pat. No. 5,278,584 to Keefe et al. and U.S. Pat. No. 5,305,015 to Schantz et al. (incorporated herein by reference). Also of interest is co-pending, co-owned U.S. patent application Ser. No. 08/921,678 (filed on Aug. 28, 1997) entitled xe2x80x9cIMPROVED PRINTHEAD STRUCTURE AND METHOD FOR PRODUCING THE SAMExe2x80x9d (Meyer et al.) which is likewise incorporated herein by reference. In this document, a number of approaches are outlined for improving the overall durability of polymeric film-type orifice plates. For example, in one embodiment, a protective coating is applied to the top surface and/or the bottom surface of the orifice plate. Representative coatings include diamond-like carbon (which is also known as xe2x80x9cDLCxe2x80x9d), at least one layer of metal (e.g. chromium, [Cr], nickel [Ni], palladium [Pd], gold [Au], titanium [Ti] tantalum [Ta] aluminum [Al], and mixtures thereof), and/or a selected dielectric, material (e.g. silicon nitride, silicon dioxide, boron nitride, silicon carbide, and silicon carbon oxide.) This approach is designed to improve the overall abrasion and deformation resistance of the thin-film orifice plate structure and avoids xe2x80x9cdimplingxe2x80x9d problems associated with these components. Furthermore, the overall durability of the completed structures is particularly enhanced through the use of DLC and the other compositions recited above.
However, other important factors must also be considered in order to produce a printhead using a non-metallic orifice plate which is capable of generating clear, distinct, and vivid printed images over prolonged time periods. For example, a condition known as xe2x80x9crufflingxe2x80x9d or xe2x80x9crufflesxe2x80x9d can occur in printheads, using thin-film polymeric (e.g. plastic) orifice plates of the type discussed herein. This condition can cause a significant deterioration in print quality if not controlled. Thermal inkjet printers of conventional design typically employ at least one wiper element (normally produced from an elastormeric rubber, plastic, or other comparable material) in order to keep the external surface of the orifice plate clean and free from residual ink and other extraneous matter including paper fibers and the like. A representative wiper system used for this purpose is described in U.S. Pat. No. 5,786,830 to Su et al. which is incorporated herein by reference. Printheads which employ thin-film organic polymer-based orifice plates are often adversely affected by the wiping process. Specifically, passage of the wiper element(s) over this type of orifice plate can cause, an xe2x80x9cupliftingxe2x80x9d of the plate structure along the edges of the orifices, thereby creating a xe2x80x9cruffledxe2x80x9d appearance with xe2x80x9cridgexe2x80x9d-like structures being formed at the peripheral edges of each orifice. This physical deformation of the orifice plate (and the resulting alteration in orifice geometry/planarity) can cause significant changes in ink drop trajectory, namely, the intended pathway to be followed by the ink drop in order to create the final printed image. These undesired changes in orifice plate geometry prevent the ink drop from traveling in its intended direction. Instead, the drop is expelled improperly and is delivered to an undesired location on the print media material (e.g. paper and/or other substrates). Deformation of the orifice plate as outlined above (including the creation of extraneous xe2x80x9cridge structures around the peripheral edges of the orifices) can also cause the collection or xe2x80x9cpuddlingxe2x80x9d of ink in these regions. This situation can further alter ink drop trajectory by causing an undesired interaction between the ink drop being expelled (particularly the terminal portion of each drop or its, xe2x80x9ctailxe2x80x9d) with collected ink adjacent the orifices. As a result, print quality degradation occurs over time. These problems are again caused by two primary factors, namely, (1) the thin, flexible nature of the organic polymer orifice plates described herein; and (2) the physical forces imposed on the orifice plates by conventional wiper structures (or other objects which may come in contact with the plates).
In summary, numerous adverse conditions are associated with xe2x80x9crufflingxe2x80x9d in a thin-film organic polymer-based orifice plate system ranging from a notable deterioration in print quality to a reduced level of printhead longevity and increased maintenance requirements. Prior to completion of the present invention, a need therefore existed for a polymeric (e.g. plastic) orifice plate system which is highly resistant to the effects of repeated wiping using one or more ink wiper elements and does not experience the ink trajectory problems caused by xe2x80x9crufflingxe2x80x9d as previously discussed. The present invention is designed to accomplish these goals in a highly effective and economical manner. In particular, the novel orifice plate and printhead designs described herein (which will be outlined in considerable depth below in the Detailed Description of Preferred Embodiments section) provide the following important benefits: (1) a substantial increase in printhead/orifice plate longevity; (2) the ability to maintain precise control over ink drop trajectory during the life of the, printhead; (3) compatibility of the claimed orifice plate with printing units which employ a variety of different wiper systems that are used to clean the printhead; (4) the avoidance of premature damage to the orifice plate notwithstanding its thin-film polymeric character, and (5) the accomplishment of these goals using a technique which avoids the deposition of additional material, layers and/or chemical compositions onto the orifice plate which can increase the cost, complexity, and overall labor requirements associated with the printhead fabrication process. The present invention therefore represents a considerable advance in the art of printhead design and image generation technology.
Further information regarding the claimed orifice plate and printhead structures (including specific data involving the technical aspects of the invention along with preferred operating parameters and representative construction materials) will be provided in the following Summary of the Invention and Detailed Description of Preferred Embodiments sections. Likewise, the particular manner in which the claimed invention provides all of the above-described benefits will become readily apparent from the detailed information presented in these sections.
Accordingly, it is an object of the present invention to provide designs for and methods of manufacturing ink-jet printheads capable of controlling ink-droplet-tail-break-off and preventing meniscus overshoot in order to overcome the puddling, pen directionality, and ruffle problems associated with thermal-ink-jet printing.
It is an object of the present invention to provide an improved printhead for use in an ink-delivery system that is characterized by high operating efficiency levels.
It is another object of the invention to provide an improved printhead having a greater overall longevity compared with conventional systems.
It is another object of the invention to provide an improved printhead that employs a polymeric (e.g. plastic) orifice plate that is thin and flexible, yet durable and resistant to deformation during the application of physical force thereto.
It is another object of the invention to provide an improved printhead that employs the novel orifice plate described above wherein the orifice plate is especially resistant to the effects of repeated wiping by ink wiper elements that are normally used for cleaning purposes.
It is another object of the invention to provide an improved printhead that employs the novel orifice plate described above wherein the orifice plate avoids xe2x80x9crufflingxe2x80x9d problems. As previously stated, xe2x80x9crufflingxe2x80x9d involves a disruption or xe2x80x9cupliftingxe2x80x9d of the orifice plate around the peripheral edges of the orifices caused by physical engagement of the plate with the wiper units mentioned above (or other structures which engage the printhead during use). This problem typically causes undesired changes in ink-drop trajectory that leads to a deterioration in print quality.
It is a further object of the invention to provide an improved printhead which employs the novel orifice plate described above that is generally characterized by improved operating efficiency, reduced maintenance problems, minimal system down-time, and uniform print quality levels over time.
It is a further object of the invention to provide an improved printhead that employs the novel orifice plate described above that can be used with a wide variety of ink ejector systems (including but not limited to those which employ thermal inkjet technology).
It is a further object of the invention to provide an improved printhead which employs the novel orifice plate described above that may be used in many different printer units including (1) xe2x80x9con-boardxe2x80x9d, self-contained ink cartridges having an internal ink supply associated therewith; (2) xe2x80x9coff-axisxe2x80x9d systems in which the printhead (and associated structures) are in operative connection/fluid communication with a remotely-located ink supply.
It is a still further object of the invention to provide an improved printhead which employs the novel orifice plate described above wherein the foregoing benefits are achieved in a highly economical manner which is especially well-suited to mass production manufacturing processes.
It is an even further object of the invention to provide an improved printhead that employs the novel orifice plate described above in which the foregoing benefits are achieved without the application of additional material layers or chemicals to the orifice plate.
A novel and highly efficient printhead structure is described below which provides numerous advantages over prior systems. As previously stated, the claimed printhead employs a specialized orifice plate of improved durability, which avoids problems associated with the passage of wiper units (or other structures) along the plate surface. The orifice plate is made from an organic polymer composition that is specially designed for this purpose. Prior systems which used thin-film orifice plates of organic polymer origin were subject to a condition known as xe2x80x9crufflesxe2x80x9d or xe2x80x9crufflingxe2x80x9d which occurred during physical contact between the orifice plate surface and various objects including ink wiper units and the like. This condition resulted in deformation of the orifice plate around the peripheral edges of the orifices (and/or adjacent regions), leading to the creation of xe2x80x9cwave-likexe2x80x9d ripples or xe2x80x9cridgesxe2x80x9d. In many cases, these deformities also caused undesired ink collection or xe2x80x9cpuddlingxe2x80x9d around the orifices. As a result, ink drop trajectory (defined above) was adversely affected, thereby causing a deterioration in print quality over time.
The present invention is designed to avoid the problems listed above while allowing thin-film polymeric orifice plate structures to be employed in a highly effective manner. Furthermore, the benefits outlined herein (including improved print quality over the life of the printhead) are achieved without the application of additional material layers to the orifice plate and/or chemical treatment thereof.
As a preliminary point of information, the present invention shall not be restricted to any particular types, sizes, or arrangements of internal printhead components unless otherwise stated herein. Likewise, the numerical parameters listed in this section and the other sections below constitute preferred embodiments designed to provide optimum results and shall not limit the invention in any respect. The claimed invention and its novel developments are applicable to all types of printing systems without limitation provided that they include (1) at least one substrate as discussed below; (2) at least one ink-ejector positioned on the substrate which, when activated, causes ink materials to be expelled on-demand from the printhead; and (3) an orifice plate having one or more ink ejection openings or xe2x80x9corificesxe2x80x9d therethrough that is positioned above the substrate having the ink ejector(s) thereon. The claimed invention shall not be considered xe2x80x9cink ejector-specificxe2x80x9d and is not limited to any particular applications, uses, and ink compositions. Likewise, the term xe2x80x9cink ejector shall be construed to cover one ejector element or groups of multiple ink ejectors regardless of shape, form, or configuration. Specific examples of various ink ejectors that may be used in connection with the invention will be listed below in the Detailed Description of Preferred Embodiments section. However, it is important to note that the present invention is especially suitable for use with ink delivery systems that employ thermal inkjet technology. In thermal inkjet printing units, at least one or more individual thin-film resistor elements are used as ink ejectors to selectively heat ink materials and expel them on-demand from the printhead. Accordingly, the novel orifice plate structures discussed below will be described in connection with thermal inkjet technology with the understanding that the invention shall not be limited to this type of system. The claimed technology is instead prospectively applicable to a wide variety of different printing devices provided that they again employ the basic structures recited above which include a substrate, at least one ink ejector on the substrate, and an orifice plate positioned above the substrate/ink ejector(s).
It should also be understood that the claimed invention shall not be restricted to any particular construction techniques (including any specific material deposition procedures or bore-forming methods) unless otherwise stated in the Detailed Description of Preferred Embodiments. For example, the terms xe2x80x9cformingxe2x80x9d, xe2x80x9capplyingxe2x80x9d, xe2x80x9cdeliveringxe2x80x9d, xe2x80x9cplacingxe2x80x9d, and the like as used throughout this discussion to describe the assembly of the claimed printhead and orifice plate shall broadly encompass any appropriate manufacturing procedures. These processes range from thin-film fabrication techniques to laser ablation methods and physical milling processes. In this regard, the invention shall not be considered xe2x80x9cproduction method specificxe2x80x9d unless otherwise stated herein.
As previously noted, a highly effective and durable printhead is provided for use in an ink delivery system. The term xe2x80x9cink delivery systemsxe2x80x9d shall, without limitation, involve a wide variety of different devices including cartridge units of the xe2x80x9cself-containedxe2x80x9d type having a supply of ink stored therein. Also encompassed within this term are printing units of the xe2x80x9coff-axisxe2x80x9d variety which employ a printhead connected by one or more conduit members to a remotely-positioned ink containment unit in the form of a tank, vessel, housing, or other equivalent structure. Regardless of which ink delivery system is employed in connection with the claimed printhead and orifice plate, the present invention is capable of providing the benefits listed above which include more efficient operation which facilitates the maintenance of high print quality levels over prolonged time periods.
The present invention as described in this section involves a special orifice plate structure produced from an organic polymer composition. The term xe2x80x9corganic polymerxe2x80x9d shall be defined and used herein in a conventional manner. Organic polymers traditionally involve carbon-containing structures of repeating chemical subunits. Likewise, the terms xe2x80x9corganic polymerxe2x80x9d and xe2x80x9cpolymerxe2x80x9d, shall be generally used in a non-limiting fashion to signify a structure which is optimally produced from one or more plastic-type compounds, examples of which will be provided below. However, the present invention shall not be restricted to any particular plastic/polymeric compounds associated with the claimed orifice plate (or orifice plate sizes, shapes, and configurations) provided that the completed orifice plate structures are able to deliver ink materials in an accurate and consistent manner.
The following discussion shall constitute a brief and general overview of the invention. More specific information involving particular embodiments, best modes, and other important features of the invention will again be recited in the Detailed Description of Preferred Embodiments section set forth below. All scientific terms used throughout this discussion shall be construed in accordance with the traditional meanings attributed thereto by individuals skilled in the art to which this invention pertains unless a special definition is provided herein.
The claimed invention involves a highly specialized printhead which employs a novel orifice plate structure. The orifice plate (which is produced from at least one organic polymer composition) is highly durable and resistant to the effects of physical contact with a number of objects including but not limited to the wiper units that are normally encountered in conventional printing systems. As a result, the orifice plate and resulting printhead are characterized by improved reliability levels and the avoidance of xe2x80x9crufflingxe2x80x9d or other deformation problems. These goals are accomplished by providing an xe2x80x9cinsetxe2x80x9d orifice plate design in which the xe2x80x9cmainxe2x80x9d ink ejection opening associated with each orifice through the plate is located beneath the top surface of the plate so that the wipers (or other physical structures) that may come in contact with the orifice plate do not directly engage this opening. The opening is therefore protected from the effects of physical abrasion and is able to maintain its overall geometric and structural integrity. This design also avoids the formation of excess ink xe2x80x9cpuddlesxe2x80x9d at the top surface of the orifice plate around the orifices so that proper ink drop trajectory is maintained. As discussed below, this xe2x80x9cinsetxe2x80x9d configuration is achieved by providing a special xe2x80x9crecessxe2x80x9d (e.g. an indentation/indented region) above each ink transfer bore through the plate (further-described below). Each recess begins at the top surface of the orifice plate and extends inwardly into the interior of the plate.
More detailed information will now be provided regarding the particular structures discussed above, with the understanding that specific information regarding the orifice plate, construction materials, dimensions, and other operational parameters will again be provided in the Detailed Description of Preferred Embodiments sections. In this regard, the present summary is designed to convey a general overview of the invention and shall not limit the invention in any respect.
In accordance with the present invention, a printhead for use in an ink delivery system is provided. As previously noted, the printhead generally includes a substrate having at least one ink ejector thereon (either directly on the substrate surface or supported by the substrate with one or more intermediate material layers therebetween, with both of these alternatives being considered equivalent and encompassed within the language of the present claims). Many different ink ejectors may be employed for this purpose without restriction although the thin-film resistor elements that are typically used in thermal inkjet printing systems are preferred. While the claimed invention shall again be described herein with primary reference to thermal inkjet technology for the sake of clarity and convenience, it shall not be limited in this respect. Next, a novel orifice plate member (or, more simply, an xe2x80x9corifice platexe2x80x9d) is provided which is produced from at least one organic polymer (e.g. plastic) composition. This orifice plate is of the general type described above and specifically disclosed in U.S. Pat. No. 5,278,584 to Keefe et al. and U.S. Pat. No. 5,305,015 to Schantz et al, as well as in co-pending, co-owned U.S. patent application Ser. No. 08/921,678 (filed on Aug. 28, 1997) entitled xe2x80x9cIMPROVED PRINTHEAD STRUCTURE AND METHOD FOR PRODUCING THE SAMExe2x80x9d (Meyer et al.) all of which are incorporated herein by reference.
The orifice plate (which is securely positioned over and above the substrate comprising the ink ejector thereon) includes a top surface and a bottom surface. The term xe2x80x9ctop surfacexe2x80x9d as used and claimed herein shall be defined to involve the particular surface associated with the orifice plate that is outermost relative to the printhead and, in effect, constitutes the xe2x80x9cexteriorxe2x80x9d surface of the orifice plate/printhead that is exposed to the external (outside) environment. It is the last xe2x80x9csurfacexe2x80x9d that the ink will pass through on its journey to the selected print media material. Likewise, it is the surface that is xe2x80x9cwipedxe2x80x9d using one or more wiping members that are employed in conventional printing units as disclosed, for example, in U.S. Pat. No. 5,786,830 to Su et al. which is, likewise incorporated herein by reference.
In contrast, the bottom surface of the orifice plate is the specific surface which is positioned within (e.g. inside) the printhead and is the initial surface of the orifice plate through which the ink enters as it is being expelled. The bottom surface is the innermost (e.g. xe2x80x9cunexposedxe2x80x9d) surface of the orifice plate which, in effect, is located between the top surface of the orifice plate and the substrate having the ink ejector(s) thereon. Finally, it is the specific surface of the orifice plate which is, in fact, adhered to the underlying printhead components including the ink barrier layer as discussed further below. Having presented these specific definitions of the top and bottom surfaces of the orifice plate that define the orientation of the plate relative to the remainder of the printhead, the novel features of the orifice plate will now be discussed.
In a preferred embodiment, at least one xe2x80x9crecessxe2x80x9d (or indented region/indentation) is provided in the orifice plate that begins at the top surface thereof and terminates at a position within the orifice plate between the top and bottom surfaces inside the main plate structure. The recess includes an upper end, a lower end, and a sidewall therebetween which defines the internal boundaries of the recess. The cross-sectional configuration of the recess (discussed in detail below), may involve many different configurations without limitation including but not limited to those that are square, triangular, oval-shaped, and circular (preferred). The upper end of the recess at the top surface of the orifice plate has a first opening therein, with the lower end of the recess comprising a second opening therein. The first opening is larger in size than the second opening, with the second opening being xe2x80x9cinsetxe2x80x9d in accordance with the design described above. The inset location of the second opening (which actually functions as the xe2x80x9cmain openingxe2x80x9d through which ink passes during image generation) provides the benefits listed above. Because of its inset and xe2x80x9cprotectedxe2x80x9d location, it is not subject to physical damage and xe2x80x9crufflingxe2x80x9d caused by physical abrasion and external forces.
Another important characteristic of the recess in a preferred embodiment is a structural relationship in which the sidewall described above is oriented at an angle of about 90 (approximately a right angle) relative to the top surface of the orifice plate member. This design provides a high degree of structural integrity and enables any physical forces applied to the top surface (first opening) of the orifice plate to be effectively confined to this region without being substantially transmitted downward into the recess and second opening. As a result, the overall integrity and planar geometry of the second opening (and surrounding structures) is maintained so that proper ink drop trajectory can occur during the life of the printhead. Likewise, the recess is either partially or (preferably) in complete axial alignment with the ink transfer bore thereunder (and vice versa), with the ink transfer bore being described in greater detail below. Specifically, the longitudinal axes associated with both the recess and bore are in alignment with each other and are coterminous as shown in the drawing figures described in the next section.
At this point, further explanatory information is warranted regarding the relationship between the first opening and the second opening wherein the first opening is xe2x80x9clarger in sizexe2x80x9d than the second opening. The term xe2x80x9clarger in sizexe2x80x9d basically involves a situation in which the cross-sectional area of the first opening exceeds the cross-sectional area of the second opening, with the term xe2x80x9careaxe2x80x9d being defined conventionally in accordance with the shape of opening under consideration. For example, in situations involving a square or rectangular opening, the cross sectional area will involve the length of the opening multiplied by its width. Regarding first and/or second openings that are circular, the cross-sectional area thereof will be defined conventionally to involve the formula xe2x80x9cxcfx80r2xe2x80x9d wherein r=the radius of the circular opening. Likewise, the conventional formulae that are used to calculate the area of other shapes (ovals, triangles, etc.) may be employed to determine the size of the first and/or second openings.
In situations involving circular first and second openings (which are preferred for numerous reasons including ease of production, the absence of angled surfaces, and the like), the term xe2x80x9clarger in sizexe2x80x9d may also involve a comparison of the respective diameter values of the openings. In an optimum embodiment designed to provide effective results, the first opening and the second opening as previously defined are both circular in cross-section, with the first opening having a first diameter and the second opening having a second diameter. In this particular embodiment, the first diameter of the first opening is preferably at least about 40 xcexcm or more longer (e.g. larger/greater) than the second diameter of the second opening. However, the present invention shall not be restricted to this numerical range or any other numerical parameters unless otherwise stated herein.
In accordance with the present invention, the first opening should be larger than the second opening for a number of reasons. By providing a first opening at the top surface of the orifice plate which is larger in size than the second opening, the transmission of disruptive physical forces from the top surface (namely, the first opening) to the second opening within the recess is again minimized in accordance with the structural relationship outlined above. While the exact physical mechanism by which this benefit is achieved is not entirely understood, it represents a novel and important feature of the invention. Likewise, the size relationship described above in which the first opening is larger in size than the second opening further facilitates proper ink drop trajectory. Any deformations in the peripheral edges of the first opening at the top surface of the orifice plate which are caused by wiping or other physical abrasion will not adversely affect the ink drop leaving the second opening in the recess in view of the larger size of the first opening relative to (1) the second opening; and (2) the ink drop passing therethrough (with ink drop size being substantially dictated by the size of the second opening within the recess). Because the ink drop is smaller in size than the first opening at the top surface of the orifice plate, the drop will not substantially engage any of the edges associated with the first opening and will therefore not be affected by any deformities (e.g. xe2x80x9crufflesxe2x80x9d) at the peripheral edges thereof.
Furthermore, the present invention shall not be restricted to any particular sizes or shapes associated with the recess, the first opening, and the second opening. While all of these structures within a given orifice are preferably uniform in cross sectional shape (e.g. circular, square, etc. from the first end to the second end), it is also contemplated that the recess and its various components could have different cross-sectional shapes at various locations. For example, the first opening at the first end of the recess could be substantially circular in cross-section while the second opening at the second end could be square in cross-section although a uniform design is again preferred and will be emphasized in the remainder of this discussion.
To achieve optimum results in a representative and non-limiting embodiment of the claimed orifice plate, the claimed recess will further comprise a bottom wall at the second end of the recess. The second opening described above passes through the bottom wall. The bottom wall is preferably planar in configuration and substantially parallel with the top surface of the orifice plate. Likewise, the bottom wall is preferably oriented at an angle of about 90xc2x0 (approximately a right angle) relative to the sidewall of the recess. As noted above, the sidewall of the recess is optimally oriented at an angle of about 90xc2x0 (approximately a right angle) relative to the top surface of the orifice plate member. In this configuration where both of the right angle relationships described above are employed in combination, the recess will be substantially cylindrical or disk-shaped as shown in the accompanying drawing figures. This design provides an especially high degree of structural integrity, deformation resistance, and the ability to maintain proper ink drop trajectory over time.
However, the claimed recess shall not be limited to the angular relationships provided above which constitute representative embodiments provided for example purposes. In situations involving the use of a recess having a bottom wall as previously described, many other variations are possible within the scope of the invention provided that the claimed recess having the desired functional capabilities is produced. For example, as clearly shown in the accompanying drawing figures and outlined in the Detailed Description of Preferred Embodiments presented below, a number of different angular relationships are contemplated involving the sidewall, bottom wall, and top surface of the orifice plate relative to each other. For example, as illustrated in the accompanying drawing figures, the sidewall associated with the recess may actually be oriented at an angle which exceeds about 90xc2x0 relative to the top surface of the orifice plate. Specifically, the angular relationship between the sidewall of the recess and the top surface of the orifice plate may involve: (1) an angle of about 90xc2x0 (approximately a right angle); or (2) an xe2x80x9cobtusexe2x80x9d angle, namely, an angle which exceeds 90xc2x0 (but is less than 180xc2x0), with a preferred, non-limiting upper limit being about 145xc2x0. Likewise, the bottom wall at the second end of the recess (through which the second opening passes) can be oriented at an angle of about 45-165xc2x0 relative to the sidewall of the recess. While the dual 90xc2x0 angle relationship between (A) the sidewall and the top surface of the orifice plate; and (B) the bottom wall of the recess and the sidewall which produces a cylindrical or disk-shaped recess is again preferred, the various angular values listed above (or others) can also be employed in multiple combinations without limitation. The selection of any given dimensions, angles, and the like in the present invention shall be determined in accordance with routine preliminary pilot testing taking into account numerous diverse factors ranging from the types of construction materials associated with the orifice plates to the manner in which the claimed printheads, will be used.
Having described the novel recess provided in the claimed orifice plate (which offers numerous benefits including but not limited to the creation of an xe2x80x9cinsetxe2x80x9d ink expulsion opening which is resistant to deformation caused by physical abrasion, wiping, and the like), the remaining portions of the orifice which reside beneath the recess will now be discussed. Positioned below the recess and in fluid communication therewith is an ink transfer bore. The ink transfer bore is in partial or (preferably) complete axial alignment with the recess and vice versa as previously discussed. As a result, ink materials expelled by the ink ejector(s) will pass upwardly through the bore, through the recess at the top surface of the orifice plate, and out of the printhead for delivery to a selected print media material (made of paper, metal, plastic, and the like). To accomplish this goal and from a functional standpoint, the ink transfer bore begins at the second end of the recess (e.g. at the second opening therein) and terminates at the bottom surface of the orifice plate member. The ink transfer bore is the first structure within the orifice plate to actually receive ink materials during the expulsion process, with the ink then passing through the bore and recess for ultimate delivery as previously noted. While a number of different structural designs may be employed in connection with the ink transfer bore as outlined below in the Detailed Description of Preferred Embodiments section, the bore is optimally uniform in cross-section along its entire length. Likewise, the bore includes a sidewall therein which is preferably oriented at an xe2x80x9cacutexe2x80x9d (less than 90xc2x0) angle relative to the top surface of the orifice plate member in order to form a substantially xe2x80x9ccone-shapedxe2x80x9d structure. This design promotes rapid and complete ink entry into and through the orifice plate. However, other sidewall designs may be employed in connection with the ink transfer bore including but not limited to those which form an angle of about 90xc2x0 (approximately a right angle) or more relative to the top surface of the orifice plate member. The selection of any given internal design relative to the claimed ink transfer bore may again be determined using routine preliminary pilot testing.
Additional data involving printhead assembly techniques and other related information will be set forth below (including a variety of construction methods which may be used to fabricate the various structural features of the orifice plate). For example, representative construction methods that can be employed to produce the claimed recess and ink transfer bore range from laser ablation methods to chemical etching and physical processing techniques in which drilling devices are used. Accordingly, a number of conventional procedures can be employed without limitation for the purposes described above. It should also be emphasized that many different printhead components, ink ejectors, size parameters, and the like are applicable to the present invention provided that the novel orifice plate is used as part of the basic printhead structure. This orifice plate again provides improved durability and proper ink drop trajectory control. In addition to the novel orifice plate recited herein, an improved xe2x80x9cink delivery systemxe2x80x9d is likewise provided in which an ink containment vessel is operatively connected to and in fluid communication with the claimed printhead discussed above. As extensively reviewed in the Detailed Description of Preferred Embodiments section, the term xe2x80x9coperatively connectedxe2x80x9d relative to the printhead and ink containment vessel shall involve a number of different situations including but not limited to the use of (1) cartridge units of the xe2x80x9cself-containedxe2x80x9d type in which the ink containment vessel is directly attached to the printhead to produce a system having an xe2x80x9con-boardxe2x80x9d ink supply; and (2) printing units of the xe2x80x9coff-axisxe2x80x9d variety which employ a printhead connected by one or more conduit members (or similar structures) to a remotely-positioned ink containment unit in the form of a tank, vessel, housing, or other equivalent structure. The novel printheads and orifice plates of the present invention shall not be restricted to use with any particular ink containment vessels, the proximity of these vessels to the printheads, and the means by which the vessels and printheads are attached to each other.
Finally, the invention shall also encompass a method for producing the claimed high-efficiency printheads. The fabrication steps which are used for this purpose involve the materials and components listed above, with the previously described summary of these items being incorporated by reference in this discussion. The basic production steps are as follows: (1) providing an orifice plate having the features listed above (and incorporated by reference herein); (2) providing a substrate comprising at least one ink ejector thereon as previously noted; and (3) securing the orifice plate member fixedly in position over and above the substrate in order to produce the printhead. In a preferred embodiment, the orifice plate will have a recess with a sidewall therein that is oriented at an angle of about 90xc2x0 (approximately a right angle) relative to the top surface of the plate and/or a bottom wall at the second end of the recess which is substantially parallel to the top surface. Other variations are possible as noted above, with the claimed orifice plate not being restricted to the specific features recited in this section. It should likewise be noted that fabrication of the recess within the top surface of the orifice plate may be undertaken before or after attachment of the orifice plate in position on the underlying portions of the printhead, with both techniques being considered equivalent. Accordingly, any statements presented herein which indicate that an orifice plate having the claimed features (including the recess) is xe2x80x9cprovidedxe2x80x9d will encompass by equivalence both of the alternatives listed above.
The present invention represents a significant advance in the art of thermal inkjet technology and the generation of high-quality images with improved reliability, speed, and longevity. The novel structures, components, and methods described herein offer many important benefits including but not limited to (1) a substantial increase in printhead/orifice plate longevity; (2) the ability to maintain precise control over ink drop trajectory during the life of the printhead; (3) compatibility of the claimed orifice plate with printing units which employ a variety of different wiper systems that are used to clean the printhead; (4) the avoidance of premature damage to the orifice plate notwithstanding its thin-film polymeric character; (5) the ability to provide a high-durability thin-film polymeric orifice plate structure which can maintain its light and thin profile while preventing the problems discussed above; and (6) the accomplishment of these goals using a technique which avoids the deposition of additional material layers and/or chemical compositions onto the orifice plate which can increase the cost, complexity, and overall labor requirements associated with the printhead fabrication process. These and other benefits, objects, features, and advantages of the invention will now be discussed in the following Brief Description of the Drawings and Detailed Description of Preferred Embodiments.
In addition to the foregoing, other embodiments of the present invention can be broadly summarized as follows. In one embodiment, a printhead for use in an ink-delivery system includes a substrate that has at least one ink ejector thereon. An orifice-plate member is positioned over and above the substrate. The orifice-plate member has at least one ink-transfer bore extending therethrough. The orifice-plate member further includes: a top surface that defines a top opening for the ink-transfer bore, a bottom surface that defines a bottom opening for the ink-transfer bore, and a counter-bore in the top surface. The counter-bore is non-concentric with the ink-transfer bore. And, the counter-bore is in fluid communication with the ink-transfer bore. By providing a non-concentric counter-bore on the top surface of the orifice-plate member, the present invention is able to control the tail break-off of expelled ink-jet droplets and thus overcome the puddling problems associated with prior-art thermal-ink-jet printing mechanisms.
In another embodiment, the ink-transfer bore defines at least one sidewall. And, when the top surface of the orifice-plate member is counter-bored, at least a portion of the sidewall is removed such that at least one part of the sidewall is thicker than at least another part of the sidewall. Thus, this embodiment can also be used to control ink-jet droplet trajectory and consequently overcome the problems of the prior art.
In a further embodiment, the counter-bore has sufficient depth to hold the meniscus and to conduct any ink puddles back to the ink-transfer bore. This minimizes and/or prevents meniscus overflow and thus improves ink-droplet-tail-break-off control.
In still another embodiment, the orifice-plate member includes a partial counter-bore instead of a full counter-bore. The partial counter-bore defines a counter-bored portion of the top surface and an un-ablated portion of the top surface. The counter-bored portion is in fluid communication with the ink-transfer bore. The un-ablated portion attracts the ink as it is delivered from the printhead. This improves ink-droplet-tail-break-off control and overcomes the limitations of the prior art.
In yet another embodiment, the counter-bore in the top surface creates a smooth and uniform edge around the ink-transfer bore in order minimize ruffles in the top surface. The counter-bore can also at least partially round the edge around the ink-transfer bore. This embodiment also improves ink-droplet-tail-break-off control and overcomes the limitations of the prior art.
Of course, the printheads, print cartridges, and methods of these embodiments may also include other additional components and/or steps.
Other embodiments are disclosed and claimed herein as well.